user_caps(5) File formats user_caps(5)

user_caps(5) File formats user_caps(5) #

user_caps(5) File formats user_caps(5)

NNAAMMEE #

 user_caps - user-defined terminfo capabilities

SSYYNNOOPPSSIISS #

 ttiicc --xx,, iinnffooccmmpp --xx

DDEESSCCRRIIPPTTIIOONN #

BBaacckkggrroouunndd Before ncurses 5.0, terminfo databases used a _f_i_x_e_d _r_e_p_e_r_t_o_i_r_e of terminal capabilities designed for the SVr2 terminal database in 1984, and extended in stages through SVr4 (1989), and standardized in the Single Unix Specification beginning in 1995.

 Most of the _e_x_t_e_n_s_i_o_n_s in this fixed repertoire were additions to the
 tables of boolean, numeric and string capabilities.  Rather than change
 the meaning of an existing capability, a new name was added.  The
 terminfo database uses a binary format; binary compatibility was ensured
 by using a header which gave the number of items in the tables for each
 type of capability.  The standardization was incomplete:

 •   The _b_i_n_a_r_y _f_o_r_m_a_t itself is not described in the X/Open Curses
     documentation.  Only the _s_o_u_r_c_e _f_o_r_m_a_t is described.

     Library developers rely upon the SVr4 documentation, and reverse-
     engineering the compiled terminfo files to match the binary format.

 •   Lacking a standard for the binary format, most implementations copy
     the SVr2 binary format, which uses 16-bit signed integers, and is
     limited to 4096-byte entries.

     The format cannot represent very large numeric capabilities, nor can
     it represent large numbers of special keyboard definitions.

 •   The tables of capability names differ between implementations.

     Although they _m_a_y provide all of the standard capability names, the
     position in the tables differs because some features were added as
     needed, while others were added (out of order) to comply with X/Open
     Curses.

     While ncurses' repertoire of predefined capabilities is closest to
     Solaris, Solaris's terminfo database has a few differences from the
     list published by X/Open Curses.  For example, ncurses can be
     configured with tables which match the terminal databases for AIX,
     HP-UX or OSF/1, rather than the default Solaris-like configuration.

 •   In SVr4 curses and ncurses, the terminal database is defined at
     compile-time using a text file which lists the different terminal
     capabilities.

     In principle, the text-file can be extended, but doing this requires
     recompiling and reinstalling the library.  The text-file used in
     ncurses for terminal capabilities includes details for various
     systems past the documented X/Open Curses features.  For example,
     ncurses supports these capabilities in each configuration:

         memory_lock
              (meml) lock memory above cursor

         memory_unlock
              (memu) unlock memory

         box_chars_1
              (box1) box characters primary set

     The memory lock/unlock capabilities were included because they were
     used in the X11R6 terminal description for xxtteerrmm(1).  The _b_o_x_1
     capability is used in tic to help with terminal descriptions written
     for AIX.

 During the 1990s, some users were reluctant to use terminfo in spite of
 its performance advantages over termcap:

 •   The fixed repertoire prevented users from adding features for
     unanticipated terminal improvements (or required them to reuse
     existing capabilities as a workaround).

 •   The limitation to 16-bit signed integers was also mentioned.  Because
     termcap stores everything as a string, it could represent larger
     numbers.

 Although termcap's extensibility was rarely used (it was never the
 _s_p_e_a_k_e_r who had actually used the feature), the criticism had a point.
 ncurses 5.0 provided a way to detect nonstandard capabilities, determine
 their type and optionally store and retrieve them in a way which did not
 interfere with other applications.  These are referred to as _u_s_e_r_-_d_e_f_i_n_e_d
 _c_a_p_a_b_i_l_i_t_i_e_s because no modifications to the toolset's predefined
 capability names are needed.

 The ncurses utilities ttiicc and iinnffooccmmpp have a command-line option “-x” to
 control whether the nonstandard capabilities are stored or retrieved.  A
 library function uussee__eexxtteennddeedd__nnaammeess is provided for the same purpose.

 When compiling a terminal database, if “-x” is set, ttiicc will store a
 user-defined capability if the capability name is not one of the
 predefined names.

 Because ncurses provides a termcap library interface, these user-defined
 capabilities may be visible to termcap applications:

 •   The termcap interface (like all implementations of termcap) requires
     that the capability names are 2-characters.

     When the capability is simple enough for use in a termcap
     application, it is provided as a 2-character name.

 •   There are other user-defined capabilities which refer to features not
     usable in termcap, e.g., parameterized strings that use more than two
     parameters or use more than the trivial expression support provided
     by termcap.  For these, the terminfo database should have only
     capability names with 3 or more characters.

 •   Some terminals can send distinct strings for special keys (cursor-,
     keypad- or function-keys) depending on modifier keys (shift, control,
     etc.).  While terminfo and termcap have a set of 60 predefined
     function-key names, to which a series of keys can be assigned, that
     is insufficient for more than a dozen keys multiplied by more than a
     couple of modifier combinations.  The ncurses database uses a
     convention based on xxtteerrmm(1) to provide extended special-key names.

     Fitting that into termcap's limitation of 2-character names would be
     pointless.  These extended keys are available only with terminfo.

RReeccooggnniizzeedd ccaappaabbiilliittiieess The ncurses library uses the user-definable capabilities. While the terminfo database may have other extensions, ncurses makes explicit checks for these:

    AX _b_o_o_l_e_a_n, asserts that the terminal interprets SGR 39 and SGR 49 by
       resetting the foreground and background color, respectively, to the
       default.

       This is a feature recognized by the ssccrreeeenn program as well.

    E3 _s_t_r_i_n_g, tells how to clear the terminal's scrollback buffer.  When
       present, the cclleeaarr(1) program sends this before clearing the
       terminal.

       The command “ttppuutt cclleeaarr” does the same thing.

    NQ used to suppress a consistency check in tic for the ncurses
       capabilities in user6 through user9 (u6, u7, u8 and u9) which tell
       how to query the terminal's cursor position and its device
       attributes.

RGB #

       _b_o_o_l_e_a_n, _n_u_m_b_e_r oorr _s_t_r_i_n_g, used to assert that the sseett__aa__ffoorreeggrroouunndd
       and sseett__aa__bbaacckkggrroouunndd capabilities correspond to _d_i_r_e_c_t _c_o_l_o_r_s,
       using an RGB (red/green/blue) convention.  This capability allows
       the ccoolloorr__ccoonntteenntt function to return appropriate values without
       requiring the application to initialize colors using iinniitt__ccoolloorr.

       The capability type determines the values which ncurses sees:

       _b_o_o_l_e_a_n
          implies that the number of bits for red, green and blue are the
          same.  Using the maximum number of colors, ncurses adds two,
          divides that sum by three, and assigns the result to red, green
          and blue in that order.

          If the number of bits needed for the number of colors is not a
          multiple of three, the blue (and green) components lose in
          comparison to red.

       _n_u_m_b_e_r
          tells ncurses what result to add to red, green and blue.  If
          ncurses runs out of bits, blue (and green) lose just as in the
          _b_o_o_l_e_a_n case.

       _s_t_r_i_n_g
          explicitly list the number of bits used for red, green and blue
          components as a slash-separated list of decimal integers.

       Because there are several RGB encodings in use, applications which
       make assumptions about the number of bits per color are unlikely to
       work reliably.  As a trivial case, for example, one could define
       RRGGBB##11 to represent the standard eight ANSI colors, i.e., one bit
       per color.

    U8 _n_u_m_b_e_r, asserts that ncurses must use Unicode values for line-
       drawing characters, and that it should ignore the alternate
       character set capabilities when the locale uses UTF-8 encoding.
       For more information, see the discussion of NNCCUURRSSEESS__NNOO__UUTTFF88__AACCSS in
       nnccuurrsseess(3).

       Set this capability to a nonzero value to enable it.

    XM _s_t_r_i_n_g, override ncurses's built-in string which enables/disables
       xxtteerrmm(1) mouse mode.

       ncurses sends a character sequence to the terminal to initialize
       mouse mode, and when the user clicks the mouse buttons or (in
       certain modes) moves the mouse, handles the characters sent back by
       the terminal to tell it what was done with the mouse.

       The mouse protocol is enabled when the _m_a_s_k passed in the mmoouusseemmaasskk
       function is nonzero.  By default, ncurses handles the responses for
       the X11 xterm mouse protocol.  It also knows about the _S_G_R _1_0_0_6
       xterm mouse protocol, but must to be told to look for this
       specifically.  It will not be able to guess which mode is used,
       because the responses are enough alike that only confusion would
       result.

       The XXMM capability has a single parameter.  If nonzero, the mouse
       protocol should be enabled.  If zero, the mouse protocol should be
       disabled.  ncurses inspects this capability if it is present, to
       see whether the 1006 protocol is used.  If so, it expects the
       responses to use the _S_G_R _1_0_0_6 xterm mouse protocol.

       The xterm mouse protocol is used by other terminal emulators.  The
       terminal database uses building-blocks for the various xterm mouse
       protocols which can be used in customized terminal descriptions.

       The terminal database building blocks for this mouse feature also
       have an experimental capability _x_m.  The “xm” capability describes
       the mouse response.  Currently there is no interpreter which would
       use this information to make the mouse support completely data-
       driven.

       _x_m shows the format of the mouse responses.  In this experimental
       capability, the parameters are

         _p_1   y-ordinate

         _p_2   x-ordinate

         _p_3   button

         _p_4   state, e.g., pressed or released

         _p_5   y-ordinate starting region

         _p_6   x-ordinate starting region

         _p_7   y-ordinate ending region

         _p_8   x-ordinate ending region

       Here are examples from the terminal database for the most commonly
       used xterm mouse protocols:

         xterm+x11mouse|X11 xterm mouse protocol,
                 kmous=\E[M, XM=\E[?1000%?%p1%{1}%=%th%el%;,
                 xm=\E[M
                    %?%p4%t%p3%e%{3}%;%' '%+%c
                    %p2%'!'%+%c
                    %p1%'!'%+%c,

         xterm+sm+1006|xterm SGR-mouse,
                 kmous=\E[<, XM=\E[?1006;1000%?%p1%{1}%=%th%el%;,
                 xm=\E[<%i%p3%d;
                    %p1%d;
                    %p2%d;
                    %?%p4%tM%em%;,

EExxtteennddeedd kkeeyy--ddeeffiinniittiioonnss Several terminals provide the ability to send distinct strings for combinations of modified special keys. There is no standard for what those keys can send.

 Since 1999, xxtteerrmm(1) has supported _s_h_i_f_t, _c_o_n_t_r_o_l, _a_l_t, and _m_e_t_a
 modifiers which produce distinct special-key strings.  In a terminal
 description, ncurses has no special knowledge of the modifiers used.
 Applications can use the _n_a_m_i_n_g _c_o_n_v_e_n_t_i_o_n established for xxtteerrmm to find
 these special keys in the terminal description.

 Starting with the curses convention that _k_e_y _n_a_m_e_s begin with “k” and
 that shifted special keys are an uppercase name, ncurses' terminal
 database defines these names to which a suffix is added:

      NNaammee   DDeessccrriippttiioonn
      ───────────────────────────────────────────────────────────────
      kDC    special form of kdch1 (delete character)
      kDN    special form of kcud1 (cursor down)
      kEND   special form of kend (End)
      kHOM   special form of khome (Home)
      kLFT   special form of kcub1 (cursor-left or cursor-back)
      kNXT   special form of knext (Next, or Page-Down)
      kPRV   special form of kprev (Prev, or Page-Up)
      kRIT   special form of kcuf1 (cursor-right, or cursor-forward)
      kUP    special form of kcuu1 (cursor-up)

 These are the suffixes used to denote the modifiers:

      VVaalluuee   DDeessccrriippttiioonn
      ──────────────────────────────────
      2       Shift
      3       Alt
      4       Shift + Alt
      5       Control
      6       Shift + Control
      7       Alt + Control
      8       Shift + Alt + Control
      9       Meta
      10      Meta + Shift
      11      Meta + Alt
      12      Meta + Alt + Shift
      13      Meta + Ctrl
      14      Meta + Ctrl + Shift
      15      Meta + Ctrl + Alt
      16      Meta + Ctrl + Alt + Shift

 None of these are predefined; terminal descriptions can refer to _n_a_m_e_s
 which ncurses will allocate at runtime to _k_e_y_-_c_o_d_e_s.  To use these keys
 in an ncurses program, an application could do this:

 •   using a list of extended key _n_a_m_e_s, ask ttiiggeettssttrr(3) for their values,
     and

 •   given the list of values, ask kkeeyy__ddeeffiinneedd(3) for the _k_e_y_-_c_o_d_e which
     would be returned for those keys by wwggeettcchh(3).

PPOORRTTAABBIILLIITTYY #

 The “-x” extension feature of ttiicc and iinnffooccmmpp has been adopted in NetBSD
 curses.  That implementation stores user-defined capabilities, but makes
 no use of these capabilities itself.

SSEEEE AALLSSOO #

 iinnffooccmmpp(1), ttiicc(1).

 The terminal database section _N_C_U_R_S_E_S _U_S_E_R_-_D_E_F_I_N_A_B_L_E _C_A_P_A_B_I_L_I_T_I_E_S
 summarizes commonly-used user-defined capabilities which are used in the
 terminal descriptions.  Some of those features are mentioned in ssccrreeeenn(1)
 or ttmmuuxx(1).

 _X_T_e_r_m _C_o_n_t_r_o_l _S_e_q_u_e_n_c_e_s provides further information on the xxtteerrmm(1)
 features which are used in these extended capabilities.

AAUUTTHHOORRSS #

 Thomas E. Dickey
 beginning with ncurses 5.0 (1999)

ncurses 6.4 2023-08-19 user_caps(5)